Current-collector and process of making the same.



E. G. GILSON.

GU-BBENT COLLECTOR AND mioofiss OF-MAKIN I APPLICATION nun) Nov, 11. 19

G THE SAME.

Patented Mar. 10, 191

UNITED STATES PATENT EMERY G-l GILSON, OF SGHENECTADY, NEW YORK, ASSIGNOR TC GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

CURRENT-COLLECTOR AND PROCESS OF MAKING THE SAME.

Specification of Letters Patent.

Patented Mar. 10, 191

Application filed November 1 7, 1911. Serial No. 660,761

To all ohom it may concern:

, Be it known that I, EMERY G. GILSON, a citizen of the United States, residing at Schenectady, county of Schenectady, State ofNew York, have invented certain new and useful Improvements in Current-Collectors and the Process of Making the Same, of which the following is a specification.

My invention relates to brushes for dynamo electric machines, particularly to molded metal brushes, and it has for its object, the provision of improved means for connecting the flexible conductors to such brushes.

Copper-graphite brdshes, such as described in my previously filed application Serial Number 570,737, filed July 7th, 1910,

- are operated at a current density very much higher than the carbon brushes, that is about 125 amperes per square inch under .normal operating conditions. This neccssr tates very much better electrical connection between the flexible conductors and the brushes.

The flexible conductors ordinarily consist of a large number offine wires or strands braided together. I have discovered that when these conductors are unbraided at theirends that these ramified ends may be molded into the body of the brush and be caused to adhere so firmly to the metal particles in the brush as to become virtually a unitary part of the brush itself.

It is important that the final firing treatment to which the brush is subjected shall take place under conditions which will permil; the conductors to retain their flexibility,

and, therefore, I preferably fire the brushes in a vacuum,

' For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing in Wl1lGl'l-- -Figure 1 is a perspective view of the brush with flexible conductors attached to lot a soft metal easily alloyable with copper, such as tin oxid or lead oxid.v This mixture is subjected to a reduction treatment which causes all but a small percentage of the metallic oxids to be reduced to the me tallic state. The reduction takes place a the expense of part of the graphite but I aim to leave about 4i. to l2 per cent. of graphite in the mixture. It is also important that a few per cent. of oxid shall remain in the mixture. The reduced mixture is molded into the form desired in the finished brush and is finally fired to consolidate the metal particles.

In accordance with my present invention, the unbraided ends of he flexible conductors are embedded in the metal-graphite mixture when it is being molded into the desired form. The brush with the embedded conductors is then tired. in a vacuum or in the presence of a neutral gas or, in general, in an environment which will not react chemically with the material of the conduc tor itself. I find that a reducing gas as was formerly commonly used to protect the brushes i during the final. firing treatment exerts'an unfavorable influence upon the flexible copper conductors so as to make them brittle. The individual strands also tend to adhere to each other and cause the conductor. to become stiff. This efi'ect is probably due to the complete reduction of oxids in the copper.

The firing treatment may take place at a temperature of about 650 C. At this temperature. the particles of metal in the body of the brush 2 attach themselves firmly to the individual wires or strands which make up the conductors 1. In my opinion this is due to the reduction of oxids in the strands and in the metal powder in immediate contact with the strands, and also to the formation of an alloy between the copper of the flexible conductors and the tin, lead or other soft metal in the brush mixture.

I find by this process that the mechanical union between the flexible wires and the body of the brush is so intimate that the flexible conductors cannot be removed from the brush without partly or completely tearing the strands of the conductor itself. The electrical contact under these conditions is of course far more rerfect than any form of mechanical union.

10 2, The precess "Wh t ii claim as new and desire 510 secure ose 2 0a s tempemfiure at which said material will eeizsoiiriate.

3. The process of making current connections to molded metal brush which con sisis in embedding the unbraided end of a go stranded. conductor in finelydivided brush material containing some oxid, compressing said in eliiliiitlld firing in a vacuum.

In witness whereof, I have hereunto set my hand this 15th day of November, 1911 25 EMERY G. GILSON.

YJibnesses i-irimr Gawain), BENJAMIN iTIULL. 

